The present invention relates to a method and apparatus for detecting, in high sensitivity, a foreign particle present on an organic protective film having an underlying circuit pattern or wiring pattern such as an X-ray exposure mask or a semiconductor wafer.
Known conventional foreign particle detecting apparatus are, for example, the apparatus described in Japanese Patent Laid-Open No. 186324/84 and an apparatus wherein the upper surface of a wafer is scanned spotwise using a laser light of 488 nm or 780 nm in wavelength, then scattered light due to the presence of a foreign particle is condensed by an integrating sphere and the thus condensed light is sensed by an optoelectro transducer to detect the foreign particle.
In such conventional foreign particle detecting apparatus, however, no consideration is given to the technical subject of detecting a foreign particle present on the organic protective film having an underlying circuit pattern or wiring pattern, in high sensitivity without being influenced by the light reflected from the circuit pattern or wiring pattern.
Though not directly related to the present invention, reference is here made to the following literature as literature showing a related art, wherein a transparent thin film called pelicle is provided on a mask to prevent a foreign particle from directly adhering onto the mask: Koizumi et al. "Hand Book for Automated System in Modern Semiconductor Factory" separate volume, Science Forum (July 25, 1984), p. 342.
However, in the case of a mask for X-ray exposure, it is necessary that the spacing between the mask and a substrate not be larger than 30 .mu.m, thus making it impossible to form pelicle on the mask, and so it is required to strictly check metallic foreign particles which do not transmit X-ray.